Basic purpose for reducing tile, porcelain, stone, and masonry materials. Continuous rim. Core-drilling - There's plenty of evidence that core-drills had been used at Giza. The basic instance being the instrument-marks found contained in the sarcophagus of the Nice pyramid. As the stone that was being reduce is granite, the surface of the drill-tip would have had to have included a material of equal or higher hardness with a purpose to reduce by the stone.<br> <br> <br> <br>